Method of treating gas cell fabric



Patented Feb. 23, 1932 UNITED STATES PATENT OFFICE WILLIAM C. CALVERT, OF C'UYAEOGA FALLS, OHIO, ASSIGNOR TO THE GOODYEAR TIRE & RUBBER COMPANY, OF AKRON, OHIO, A CORPORATION 01 OHIO METHOD OF TREATING GAS CELL FABRIC No Drawing. Application filed January 14, 1932, Serial .No. 586,593, and in Canada December 29, 1980.

My invention relates to a treated fabric adapted, among other things, for use in gas cells for lighter-than-air craft. More particularly, it relates to a fabric so treatedas to possess, in addition to its inherent flexibility, a greatly increased resistance to the passage of gases and liquids therethrough and an enhanced durability. The invention also has relation to the provision of improved coating media for fabrics.

One of the objects of my'invention is to provide a treated fabric having an exceptionally high degree of flexibility and durability; another, to provide a fabric which offers unusually great resistance to the diffusion of gases and to the passage of liquids therethrough. Still another object is to provide coating material which is inexpensive toprocureand which may be applied to the fabric quickly, uniformly and economically. Other objects will be apparent as the description of the invention proceeds.

For illustrative purposes, my invention will be hereinafter described as ap lied to a gas cell for lighter-than-air cra t, but it should be understood that the invention rather than being limited thereto may be em: ployed wherever a fabric of the properties of that herein described is desired.

The gas'cells of lighter-than-air craft are usually constructed of light, strong and closely woven cotton or silk fabrics, which, in order to prevent diffusion of the inflating gases, are coated with a thin layer of a relatively impermeable material. This material, in addition to being comparatively impermeable, should be suflicientl'y tough, elastic and flexible to withstand .a reasonable degree of such stretching and flexingas that to which the fabrics of gas cells are-usually subjected. Furthermore, it should adhere permanently to the fabric and should retain its desirable properties for an indefinite pe-. riod of time. In addition to possessing these physical properties, it should be sufiiciently inexpensive to procure land to apply to permit of its use.on the greatsurfaces found in gas cells of lighter-than-air craft. 4

Heretofore, gold beaterls skin, which is a thin, light, highly impermeable membrane,

taken from the viscera of cattle, and rubber have been considered the two materials most concerned, gold beaters skin has heretofore r been consldered the more satisfactory material of the two. Unfortunately, it is expensive to procure and because of the. small size of the units in which it is obtained, the application thereof to fabrics entails a great amount of labor. In contradistinction to this, rubber is relatively inexpensive to obtain and may be applied to the fabric easily'and economieally by means of machinery. However, it offers only moderate resistance to diffusion of such light and highly difl'usive gases as hydrogen and helium.

My invention contemplates, among other things, the provision of a coating material for gas cells which offers a resistance to the diffusionof inflating gases equal, or even superior, to that of gold beaters skin. At the same time it possesses almost equal flexibility and elasticity, so that it is not readily cracked 1 or broken by flexing and tensioning the fabric. Furthermore, its initial cost is relatively low and it may be spread quickly and economically upon the fabric base.

The invention involves the discovery that polyglycerol and/or polyglycol, when incorporated either alone or together with latex (the concentration ranging from that of ordinary latex to much higher ones in a maare'highly satisfactory from the standpoint of flexlbility, elasticity and resistance to diffusion of inflating gases and which have the further advantage that the component materials may be obtainedreadily and economically.

In the case of gelatine, glue and agar agar,

the composition inafy conveniently be prepared in the form '0 an aqueous solution or suspension; in the case of viscose, from which ed out, may be incorporated in any of they ber.

the cellulose is regenerated at a later stage of the process, it is sufiicient to mix the polyglycerol and viscose together. So prepared, the composition may be applied directly to the surface of the fabric base by spreading, spraying, brushing or by any other convenient method. If desired, it may-be made into thin sheets corresponding in width to thatof the fabric, to which it may be attached by means of a suitable rubber cement or other binder. The latter method, while not so economical as the other methods above mentioned, is nevertheless far more desirable than the process formerly practiced of applying gold beaters skin to the fabric in small units.

Polyglycerol may be prepared by heating commercial glycerine, either the C. P. or the dynamite grade, at 280 degrees C. for a minimum period of 30 minutes, thereafter evaporating the resulting material by dry heat until the temperature reaches approximately 300 degrees C. The initial heating, as desired, may be with or without a catalyst,

- although where such is employed it may conveniently be either sodium bicarbonate, 0.2%, or sodium hydroxide, 0.5%. This and other methods of preparing polyglycerol, particularly diglycerol, are discussed at pages 303 and 304 of Glycerol and the Glycols by James W. Lawrie, published in New York in 1928 by The Chemical Catalog Company, Inc. as a part of the A. C. S. monograph series. A similar discussion is found in Lewkowitschs Chemical Technology and Analysis of Oils, Fats and Waxes, 5th edition, Volume I, page 262.

Althoughpolyglycerol, as elsewhere pointcoating materials above mentioned, only its use with gelatin will be described in detail. Approximately 50 grams of polyglycerol prepared as above outlined are incorporated into 750 cc. of an aqueous gelatin solution containing 25 grams of commercial gelatin. Experiments have shown that the proportion of polyglycerol may even be increased to two and one half times that of the gelatin Without impairing the useful properties of the product. The material thus preparedmay be applied to gas cell fabrics of practically any construction. For example, the fabric may consist of a plurality of plies cemented together. The surface of the foundation fabric may be uncoated or it may be covered, prior to the application of the polyglycerolgelatine composition, with a coating of rub- The latter may be calendered into the fabric or-may be appliedin the form of latex or rubber cement.

. The polyglycerol composition is spread in successive films by any of the methods previously mentioned until afilm of the proper thickness has been built up. Where it is brushed on, it is sufiicient for most purposes 'tinuously.

'to abrasion and other forms of wear.

cal spreader operating against a drum or the like, enabling the process to be carried on con- Preferably, each film is dried before the application of the succeeding one,

the fabric being meanwhile subjected to tension by spreading frame or tentering machine.

A preferred method of practicing this part of the invention is disclosed and claimed in my copending application Serial No. 442,696, filed April 8, 1930, for Gas cell fabric.

If desired, the fabric so prepared may be passed through a tanning bath, either after the application of each film or at the conclusion of the coating process. Any tanning agent, such as a solution of 10% para formaldehyde or a solution of alum of suitable concentration may be used for this purpose. This operation is not essential if the fabric is to be employed in the construction of gas cells for aircraft of the Zeppelin type, in which the gas containers are enclosed within an outer waterproof envelope. It is, however, desirable to add to the coated fabric, for the purpose of waterproofing it and increasing its resistance to abrasion, a final coating of a flexible surfacing material such as a varnish having a drying oil base, a nitrocellulose lacquer, parafiin dissolved in benzene or toluene, or a rubber cement.

Thereafter, it is desirable, although not strictly necessary, to cure the fabric so prepared. Where an air-curing rubber cement is employed in the fabrication thereof, it is merely necessary to allow the fabric to stand,

of 24 hours or longer in order to cure the rubber and remove the volatile ingredients. In either case, the bonding effect is enhanced and the fabric as a whole made more resisltargt a, rics so prepared are not only light, comparatively impermeable and highly flexible, but capable of retaining such properties for an indefinite length of time.

This application is a continuation in part of my prior application Serial No. 347,182, filed March 14, 1929. Although I have described in detail herein, only the preferred forms which the invention may assume, it will be apparent to those skilled in the art that it is not limited thereto, but that various novelty reside in the invention.

' condensation What I claim is: K

1. A fabric adapted for use in the'construction of gas cells of lighter-than-air craft consisting of a light but closely woven textile material coated with a continuous film of a composition comprising gelatin and polyglycerol.

2. A material adapted for use in the construction of gas cells for lighter-than-air craft comprising a textile fabric coated with a continuous film of a material containing gelatin and polyglycerol, the polyglycerol constituting the major ingredient in the material.

3. A gas cell fabric composed of light, closely woven material coated with a thin continuous filmof material highly resistant to the diffusion of inflating gases and containing p'olyglyceroL- 4. A woven gas cell fabric coated with a continuous film of a material containing a product of a polyhydric alcohol and gelatin.

5. A gas cell for lighter-than-air craft composed of light, closely woven fabric coated with a continuous film of a compound containing approximately one part of gelatin and two parts of polyglycerol.

6. A gas cell for lighter-than-air craft composed of a light but closely woven fabric coated with a continuous film of a compound containing approximately 1 part of gelatin and approximately 2 to 2 parts of poly- .glycerol. 4

7. A gas cell for lighte'r-than-air craft composed of a light, closely woven fabric the approximate proportions of 1 part of gela material selected from a group consisting of gelatin, agar agar, glue and regenerated cellulose.

13. A fabric adapted for use in gas cells comprising a light, closely woven material coated with a thin, continuous film which is highly resistant to the diffusion of gas therethrough and which contains polyglycerol, latex and a material selected from a group consisting of gelatine, agar agar, glue and regenerated cellulose.

14. A woven gas cell fabric coated with a continuous film containing a proteinous material and the condensation product of a-polyhydric alcohol.

15. A woven gas cell fabric coated with a continuous film containing a condensation product of a polyhydric alcohol and a material selected from a group consisting of gelatin, agar agar, glue and regenerated cellulose.

In witness whereof, I have hereunto signed my name.

Signed at Akron, in the county of Summit and State of Ohio, U. S. A., this 13th day of January, 1932.

WILLIAM C. CALVERT.

coated with a continuous film of a compound 7 consisting essentially of gelatin and polyglycerol, the polyglycerol comprising the ma- 3' or constituent in the composition.

8. A method of treating fabric of the class described which consists in applying to a surface of the fabric a plurality of relatively thin superimposed films of a composition material containing proteinous material and polyglycerol.

9. A method of preparing fabric of the class described which consists in providing a closely woven fabric and applying to one side thereof a relatively thin gasproof coating of composition material containing polygly'cerol. v

10. A method of treating fabric of the class described which consists in applying to the fabric a relatively thin surface film of composition material containing gelatin and polyglycerol in the approximate proportionsof 1 part of gelatin to 2-21 glycerol.

11; A method of treating fabric of the class parts of polydescribed which consists in applying to a surface of the fabrica plurality of relatively thin superimposed films of'a composition material containing gelatinland polyglycerol in 

